Packing blockage and power generation of constructed wetland coupled microbial fuel cell systems using biochar as electrode and filler with different ratios.

• We made CW-MFCs with 100% biochar electrodes and biochar fillers by reeds harvested in nature. • The addition of biochar filler can improve the electricity generation performance but may cause severe filler clogging. • Adding biochar filler can improve the denitrification effect. This article investigated the electrochemical performance, water purification capacity and packing clogging of constructed wetland-microbial fuel cells coupled reactors (CW-MFCs). The CW-MFCs-B (B = 100 % biochar filler) reactor performed the best under intermittent conditions, with a power density of up to 33.7 mW/m2. Regarding TOC removal, CW-MFCs-G (G = no biochar filler) was the least effective when the system was in continuous flow. The effect of the other two reactors with biochar filler addition (BG = 50 % and B = 100 %) was similar, indicating that the biochar functioned well as the CW filler to remove organic matter. Regarding NH 4 +-N removal, removal rates varied at different HRTs: HRT = 2 days > intermittent flow > HRT = 0.5 days. Among them, CW-MFCs-B was the most effective, with a maximum of 65.10 %. The clogging index Φ b of the three reactors were 2.83 (B), 1.77 (BG), and 0.72 (G). The CW-MFCs-B reactor showed good effluent treatment and had the best electricity production but the most severe clogging. There may be a certain connection between H 2 O 2 concentration and the degree of CW clogging. CW-MFC with biochar electrode and gravel filler may be suitable for long-term operation. [ABSTRACT FROM AUTHOR]